A social real-time collaboration system (also called social collaboration system) is a system in which different devices or terminations for different types of communication are synchronized, in which corresponding signaling occurs between the devices. Within the social real-time collaboration systems, like in the “Circuit®” system, in particular multiple terminals belonging to the same user are linked together for communication. In this way, the user can chat and telephone simultaneously (parallel), or data can be transmitted in part via a desk telephone belonging to the social real-time collaboration system on one hand and via a personal computer connected in parallel on the other hand. It is characteristic of the centralization of these participants under one system that such advantages are provided by means of synchronization between the terminals. Such synchronization is not known in an open environment (heterogeneous environment), that is, if two different network systems that work with different network technologies are connected.
In everyday communications, often a first person would like to call a second person and first attempts it using the landline telephone. At the same time, the other person is using the cellular network to telephone a third person, so the person calling on the landline does not notice this. Instead it will just go unanswered. If necessary, the caller will attempt the cellular telephone as an alternative, and find out only then that it is busy.